Abstract
A femtosecond pump-probe setup is described that is optimised for broadband transient reflectivity experiments on solid samples over a wide temperature range. By combining high temporal resolution and a broad detection window, this apparatus can investigate the interplay between coherent collective modes and high-energy electronic excitations, which is a distinctive characteristic of correlated electron systems. Using a single-shot readout array detector at frame rates of 10 kHz allows resolving coherent oscillations with amplitudes <10−4. We demonstrate its operation on the charge-transfer insulator La2CuO4, revealing coherent phonons with frequencies up to 13 THz and providing access into their Raman matrix elements.
Highlights
One of the most intriguing fields of research in contemporary condensed matter physics is the investigation of many-body effects in strongly correlated quantum systems
We demonstrate its operation on the charge-transfer insulator La2CuO4, revealing coherent phonons with frequencies up to 13 THz and providing access into their Raman matrix elements
In this regard, this methodology represents a fundamental step prior to the application of more sophisticated structural probes like ultrafast x-ray and electron diffraction
Summary
One of the most intriguing fields of research in contemporary condensed matter physics is the investigation of many-body effects in strongly correlated quantum systems. When some external parameter (e.g., temperature, pressure, magnetic field) is varied, the change of the electron-boson coupling can be followed through the phase diagram.16 To assess this phenomenology, one needs to develop an instrument which is capable of: (i) achieving a high time-resolution, to detect possibly excited low-energy coherent bosonic modes of the material under study; (ii) offering a broad detection window covering the region of the high-energy interband transitions of the solid, where the bosonic modes are likely to resonate; (iii) providing a high versatility in the determination of the nonequilibrium optical properties under varying experimental conditions; (iv) achieving a high signal-to-noise ratio to clearly identify the spectro-temporal features characterizing the ultrafast optical response. Intriguing possibilities for the future implementation of low-temperature time-resolved broadband magneto-optical measurements and time-resolved spectroscopic ellipsometry.
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